1. Field of Invention
The present invention relates to a wafer packaging method.
2. Description of Related Art
With the advance in glass cutting technology, glass manufacturers are able to manufacture glass sheets with thickness under 400 μm. When an image sensor wafer, e.g., a CMOS wafer, is packaged, a glass sheet is needed to cover the surface of the wafer for the wafer protection. Although a thinner glass sheet can provide a better light transmittance and improved image detecting ability of chips formed from the diced wafer, the strength of the thin glass is more likely of lacking mechanical strength and having warpage, so as to increase the difficulty in the manufacturing process of the wafer.
FIG. 1A is a schematic view of a glass sheet 210 when being adhered to a wafer 220 in the prior art. FIG. 1B is a schematic view of the glass sheet 210 shown in FIG. 1A in a state of being adhered to the wafer 220. As shown in FIG. 1A and FIG. 1B, due to the small thickness of the glass sheet 210, the warpage of the glass sheet 210 may happen before the glass sheet 210 is placed on the wafer 220. It is difficult to align the glass sheet 210 with the wafer 220, which may introduce a shift of the glass sheet 210 on the wafer 220. As a result, the glass sheet 210 may protrude from the wafer 220 by one side, and an area A in the figure is easily cracked.
FIG. 2A is a schematic view of the glass sheet 210 shown in FIG. 1B in a state of being adhered to a tape 230. FIG. 2B is a schematic view of the wafer 220 shown in FIG. 2A after being ground (referred to as the verb tense of the word “grind”). As shown in FIG. 2A and FIG. 2B, after the glass sheet 210 is adhered to the wafer 220, the tape 230 for increasing strength is first required to adhere to the glass sheet 210, and then to perform a grinding process on the wafer 220. However, since the glass sheet 210 is not precisely aligned with the wafer 220, it is easily, in cutting the tape 230, to crack the area B of the glass sheet 210 protruding from the wafer 220, so as the area C of the wafer 220 protruding from the glass sheet 210.